1. Field of the Invention
The present invention relates to an infrared sensor of a rear surface irradiation type.
2. Description of the Related Art
Recently, uncooled thermal infrared array sensors, thermal infrared line sensors and so forth using bolometers, thermopiles, diodes and so forth have been aggressively developed (for example, see Japanese Laid-Open Patent Application No. 2000-114607).
As a thermal infrared sensor, a thermal infrared sensor of a rear surface irradiation type is known.
An infrared sensor part included in such a thermal infrared sensor of a rear surface irradiation type has a configuration shown in FIGS. 1A and 1B, for example. FIG. 1A shows a sectional view of the infrared sensor part 10. FIG. 1B shows a plan view of the infrared sensor part 10. FIG. 1A shows the sectional view taken along the A-A′ line in FIG. 1B. Note that FIGS. 1A and 1B show the infrared sensor part 10 in a magnifying way, which is a part of an infrared sensor as shown in FIG. 2, for example.
In the infrared sensor part 10, an infrared absorption part 3 and a temperature sensor part 4 are formed on a substrate 1. The infrared absorption part 3 is a thin film made of a material that absorbs infrared rays. The temperature sensor part 4 is provided for the purpose of obtaining a change in the temperature occurring as a result of the infrared absorption part 3 absorbing infrared rays. In FIGS. 1A and 1B, an example of employing the temperature sensor part 4 of a thermopile type is shown.
The infrared absorption part 3 and the temperature sensor part 4 are formed on a heat insulated structure member 2 that is formed for the purpose of improving the heat insulation property with respect to the substrate 1 and improving the sensitivity of the infrared sensor part 10. The heat insulated structure member 2 has such a configuration that a thin film part 6 is supported to create a hollow state thereunder. For this purpose, as shown FIG. 1B, such a configuration may be provided that beam parts 5 support the thin film part 6. Openings 7 are provided at the four corners as shown in FIG. 1B, and determine the shapes of the beam parts 5 and the thin film part 6. The infrared absorption part 3 is formed integrally with the thin film part 6 of the heat insulated structure member 2. Further, a part of the substrate 1 below the heat insulated structure member 2 is removed, as shown in FIG. 1A.
In the infrared sensor including the above-mentioned infrared sensor part 10, the infrared sensor part 10 is formed on the substrate 1, and a peripheral circuit 11 is formed around the infrared sensor part 10 as shown in FIG. 2, for example.
Further, also as shown in FIG. 2, a through hole 12 is formed in the substrate 1 below the infrared sensor part 10 to expose the heat insulated structure member 2. Through the through hole 12, infrared rays are transmitted. Therefore, in the configuration shown in FIG. 2, the angle of field B of the infrared sensor is determined by the thickness of the substrate 1 and the opening size of the through hole 12.